Current through a Wire

[mic1992]

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Hello,
I am having a difficult time with magnetic field/current/etc.

Two horizontal current-carrying wires are parallel. If the current is directed to the right for both, the wires are attracted to each other. With the right hand rule: the magnetic field is pointed out of the page for the bottom wire and into the page for the top wire? And thus they are attracted to each other? Thank you very much for your time!

 

[dudewheresmymd]

see below for revised post

 

[milski]

If . and X are depicting the fields out/into the page, they're wrong. The magnetic field generated around a straight current wire is something like a loop around the wire. In your case, the field above each of the wires is out of the page and below the wire into the page.

Then you need one more step with the right hand rule, having the direction of the current and the direction of the field, you can determine the direction of the force. That should lead you to the fact that the two wires indeed are attracting each other.

Like here:

 

[dudewheresmymd]

see revised post below.

 

[Laureatebarrel]

.........................................
________>>>____________ (force on top wire due to bottom wire out of page ".") (right hand rule thumb to right, fingers out of page force down)
XXXXXXXXXXXXXXXXXX

.........................................
_________>>>>__________ ( force on bottom wire due to top wire into the page Xs) (right hand rule, thumb to right, fingers into page, force up)
XXXXXXXXXXXXXXXXXX

Thus, the wires are attracted to each other since force on top wire due to bottom points down and force on bottom due to top wire points up. You have your magnetic field directions mixed up. See above for clarification. You derive the magnetic forces for each wire by using the wrap around right hand rule...the magnetic field that the top wire produces is responsible for the force on the bottom wire and the magnetic field that the bottom wire produces is responsible for the force on the top wire.

It's not the force, it's the magnetic field due to each wire that you are describe. To find the force, you need to do right hand rule one more time with the magnetic field and the current! That will show the upper wire with downward magnetic force and the bottom wire with upward magnetic force.

 

[dudewheresmymd]

I edited post again for clarity. Sorry 3 hours of sleep last night.

( The dots near the top wire are caused by the magnetic field generated by the current flowing through the bottom wire)
(The crosses near the bottom wire are caused by the magnetic field generated by the current flowing through the top wire)

.........................................
.........................................
________>>>____________ (magnetic field in the area of the top wire produced by the current flowing through the bottom wire is out of the page)
(right hand rule: thumb to right, fingers out of page, palm pointed down)



_________>>>>__________ (magnetic field in the area of the bottom wire produced by the current flowing through the top wire is into the page)
XXXXXXXXXXXXXXXXXX (right hand rule: thumb to right, fingers into page, palm pointed upwards)
XXXXXXXXXXXXXXXXXX


Wires attract b/c forces are in opposing directions!